A working ballast will power up the bulb within 15 minutes, but you'll get near instant illumination, the 15 minute part is just to achieve full brightness.
Make sure your AC connector is in the right input, 120v or 240v. They fit both just the same unfortunately.
Make sure if it has a HPS or MH switch (or even an off switch) that it isnt set to the wrong one. Flower = red = hps, and Veg = White = MH
Does the ballast hum? Check outlet or circuit if it doesnt. If it does, replace the bulb.
You do also need to have a 1000w bulb with a 1000w ballast. If you try any other wattage in there, it wont work.
My guess - bulb is bad. I had one that wouldnt turn on today, swapped the bulb, and magic...........